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![Classical interpretation and reinterpretation of the San Jacinto Valley stepover. (a) The conventionally accepted configuration of the San Jacinto Valley stepover that led to the segmentation model for the Casa Loma and Claremont faults (Working Group on California Earthquake Probabilities, 1995, 2007; Sanders and Magistrale, 1997; Field et al., 2009); the fault lines are adopted from USGS Quaternary fault and fold database; (b) annotated geomorphic features that delineate the active fault strands (scarps, pressure ridges, and lineaments) superposed on LiDAR and Google Earth images; (c) interpretation of the primary active faults within the San Jacinto Valley stepover zone: bold lines, interpreted as the main fault zone; thinner lines, secondary fault strands; dashed lines, lineaments with no obvious vertical or lateral offset. The transfer zone consists of several cross‐basin faults that have been identified at the northern end of Casa Loma fault in Mystic Lake. The color version of this figure is available only in the electronic edition.]()
![Fault map of the San Jacinto Valley area showing the location of the Quincy, Mystic Lake, and Hog Lake paleoseismic sites. Local city centers (black squares) and major highways (white lines) are shown for reference. Inset map shows the southern San Andreas fault system with paleoseismic sites represented as black dots. PA, Pallet Creek; WT, Wrightwood; CC, Cajon Creek; PT, Pitman Canyon; PL, Plunge Creek; BF, Burro Flats; TP, Thousand Palms; ML, Mystic Lake; HL, Hog Lake; CMT F, Claremont fault; CL F, Casa Loma fault; BR F, Buck Ridge fault; C F, Clark fault; CC F, Coyote Creek fault; LA, Los Angeles; SA, Santa Ana; and R, Riverside.]()
![Figure 5. Gravity and magnetic model across the Lakeview Mountains pluton along profile B–B′ (Figs. 1 and 2). D—densities in kg/m3. S—susceptibility in 10−3 SI units. Gray patterned bodies are of western Peninsular Ranges batholith affinity; shades of gray, Lakeview Mountains pluton (the darker shades of gray represent denser and more magnetic bodies); white bodies, eastern Peninsular Ranges batholith. Stippled pattern denotes Cenozoic sedimentary deposits, and patterned white areas are middle to lower crust. Curve labeled “alternate” on upper panel is that produced by placing non-magnetic rocks beneath San Jacinto Valley. CF—Claremont fault; CLF—Casa Loma fault; V.E.—vertical exaggeration.]()
![The Claremont–Casa Loma stepover of the northern San Jacinto fault, southern California: a real‐world example of a stepover with an intermediate fault strand between the primary segments. The rightmost strand is the Claremont, and the leftmost is the Casa Loma. The small fault between the two main strands, in the upper left of the image, is the Farm Road strand (U.S. Geological Survey and California Geological Survey, 2010). The inset map provides a broader view of the geographical location.]()
![Close up of the northern SJF zone with geometry based on the U.S. Geological Survey (USGS) Quaternary Faults Database (see Data and Resources). The Claremont–Casa Loma stepover is circled in green. The Claremont strand is the more northeasterly of the two; the Casa Loma is to the southwest. The small fault within the northern end of the stepover is the Farm Road strand.]()
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![Example paths of rupture propagation given earthquake initiation points (stars) on two major southern California faults. Rupture starting at Bombay Beach (eastern star) is modeled on the San Andreas fault (SAF) for its full length. Rupture northward on the San Jacinto fault (SJF, western star) begins at the Casa Loma stepover then transitions to the SAF either directly, or by a short section of the Lytle Creek fault. Rupture may also extend south from the Casa Loma starting point. The color version of this figure is available only in the electronic edition.]()
![The fault strength parameter S for a N7°E‐oriented regional stress field with an input stress drop of 5.5 MPa and an input S of 0.6. Different input values of S and stress drop would produce different effective S values but not a different pattern of relative high S to relative low S. The actual S value on most parts of the fault is not equal to the input S value. The Claremont strand has less variation in S overall than the Casa Loma strand does, and the bands of particularly high or particularly low S are wider on the Casa Loma strand than on the Claremont strand.]()
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![UCERF3‐based rupture length probabilities for rupture with one end at the San Jacinto Casa Loma step. (a) Individual annual rupture rates (probabilities) (stars) and incremental magnitude–frequency distribution (MFD, solid line, binned at 0.1 magnitude units) of all ruptures in UCERF3 fault model 3.1 having one end at the Casa Loma step of the SJF (west star, Fig. 6). (b) The solid line is corresponding complementary cumulative distribution (CCD) (solid line) of rupture length for ruptures in (a). Dashed line shows the length CCD for the fraction of ruptures starting at the step. Compared to the solid line, individual rupture probabilities are reduced by the number of alternate initiation points (subsections) in which rupture might have started. The fault geometric CCD is replotted from Figure 8c. The fault geometric approach predicts longer ruptures than UCERF3 for 75% of ruptures starting at the step. The CCD curves cross at 62 km and 25% probability. 18% of UCERF3 ruptures grow to 80 km or longer, compared to 6% for the fault geometric estimate. (c) CCD for rupture magnitude for the reduced CCD and fault geometric curves in (b). A GR conditional probability of magnitude is shown for reference (dotted). The fault geometric approach predicts larger median magnitudes for ruptures starting at the step than either UCERF3 or the GR. The color version of this figure is available only in the electronic edition.]()
![Mesh of the SJF, generated with FaultMod (Barall, 2009), as used in our dynamic models. The parts of the fault that are able to rupture are marked in white. The Claremont strand is to the left in this figure, the Casa Loma to the right, and the Farm Road is between them. The grid size is 100 m in the near field, and 400 m in the far field.]()
![Map of the San Jacinto fault (SJF) zone, with a geometry based on the U.S. Geological Survey (USGS) Quaternary faults database (USGS, 2010; see Data and Resources). The Claremont strand is shown in blue, the Farm Road strand in red, and the Casa Loma–Clark strand in black. Other strands of the SJF are shown in yellow, and other Quaternary faults are shown in gray. The cities are indicated with blue dots. The area of the present study is enclosed in the green box.]()
![Geometric and cumulative penalties at subsection boundaries for rupture northwest and southeast from the San Jacinto Claremont–Casa Loma stepover. (a) Individual step (“+” and dashed) and bend passing probabilities (“o”) on the paths of rupture extending (a) unilaterally northwest onto the SAF by Lytle Creek to the SAF. (b) Cumulative probability of length for the intersection penalties in (a). Arrows mark section intersections. For lengths up to 300 km, the GR (heavy dashed line) predicts lower conditional probabilities of a given rupture length. (c) Cumulative probability for an alternate path where the SJF connects directly to the SAF directly from the San Bernardino strand of the SJF. (d) Conditional probability of rupture length unilaterally southeast from the Casa Loma starting point. The fault‐geometric estimate of probability of any length bilateral rupture is the product of the two unilateral estimates. Section names: Anza, San Jacinto Anza; Borr, Borrego; Coyo, SJF Coyote Creek section; LY, Lytle Creek; SJC, San Jacinto stepover combined; SHills, Superstition Hills; SJV, San Jacinto Valley; SJSB, San Jacinto San Bernardino; SMntn, Superstition Mountain. Other abbreviations given with Figure 7. The color version of this figure is available only in the electronic edition.]()
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1-20 OF 119 RESULTS FOR
Casa Loma fault
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Journal Article
GEOLOGIC FEATURES OF A SECTION ACROSS THE CASA LOMA FAULT, EXPOSED IN AN AQUEDUCT TRENCH NEAR SAN JACINTO, CALIFORNIA Available to Purchase
Journal: GSA Bulletin
Publisher: Geological Society of America
Published: 01 October 1962
GSA Bulletin (1962) 73 (10): 1293–1296.
...RICHARD J PROCTOR Abstract The active Casa Loma fault, which closely parallels the San Jacinto fault, was briefly exposed in an aqueduct trench across San Jacinto Valley in Southern California. Physical features, a gravity survey, profile levels, and groundwater data show that San Jacinto Valley...
Journal Article
A seismic refraction and reflection study across the central San Jacinto Basin, Southern California Available to Purchase
Journal: Geophysics
Publisher: Society of Exploration Geophysicists
Published: 01 October 1996
Geophysics (1996) 61 (5): 1258–1268.
... bounded by two strands of the San Jacinto fault zone: the Claremont Fault on the northeast and the Casa Loma Fault on the southwest. We present a case study of shallow structure (less than 1 km) in the central basin. A 2.75-km refraction line running from the northeast to southwest across the regional...
Journal Article
Straightening of the Northern San Jacinto Fault, California, as Seen in the Fault‐Structure Evolution of the San Jacinto Valley Stepover Available to Purchase
Publisher: Seismological Society of America
Published: 01 June 2013
Bulletin of the Seismological Society of America (2013) 103 (3): 2047–2061.
...Gayatri Indah Marliyani; Thomas K. Rockwell; Nathan W. Onderdonk; Sally F. McGill Abstract We investigate a releasing stepover between the Casa Loma and Claremont strands of the northern San Jacinto fault zone to evaluate the late Quaternary structural evolution of the fault zone, and to assess...
FIGURES
Journal Article
LiDAR and Field Observations of Slip Distribution for the Most Recent Surface Ruptures along the Central San Jacinto Fault Available to Purchase
Publisher: Seismological Society of America
Published: 01 April 2012
Bulletin of the Seismological Society of America (2012) 102 (2): 598–619.
... on strands of the SJF alone ( DeMets and Dixon, 1999 ; Bennett et al. , 2004 ; Fialko, 2006 ). Although the SJF zone comprises many discrete faults, the Clark–Casa Loma strand is the longest and most continuous segment at nearly 120 km in total length, stretching from the San Felipe Hills...
FIGURES
Includes: Supplemental Content
Image
Classical interpretation and reinterpretation of the San Jacinto Valley ste... Available to Purchase
in Straightening of the Northern San Jacinto Fault, California, as Seen in the Fault‐Structure Evolution of the San Jacinto Valley Stepover
> Bulletin of the Seismological Society of America
Published: 01 June 2013
Figure 2. Classical interpretation and reinterpretation of the San Jacinto Valley stepover. (a) The conventionally accepted configuration of the San Jacinto Valley stepover that led to the segmentation model for the Casa Loma and Claremont faults ( Working Group on California Earthquake
Image
Fault map of the San Jacinto Valley area showing the location of the Quincy... Available to Purchase
in Evidence for Seven Surface Ruptures in the Past 1600 Years on the Claremont Fault at Mystic Lake, Northern San Jacinto Fault Zone, California
> Bulletin of the Seismological Society of America
Published: 01 February 2013
sites represented as black dots. PA, Pallet Creek; WT, Wrightwood; CC, Cajon Creek; PT, Pitman Canyon; PL, Plunge Creek; BF, Burro Flats; TP, Thousand Palms; ML, Mystic Lake; HL, Hog Lake; CMT F, Claremont fault; CL F, Casa Loma fault; BR F, Buck Ridge fault; C F, Clark fault; CC F, Coyote Creek fault
Image
Figure 5. Gravity and magnetic model across the Lakeview Mountains pluton a... Available to Purchase
in Geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the San Jacinto fault zone, southern California
> GSA Bulletin
Published: 01 September 2004
-magnetic rocks beneath San Jacinto Valley. CF—Claremont fault; CLF—Casa Loma fault; V.E.—vertical exaggeration.
Image
The Claremont–Casa Loma stepover of the northern San Jacinto fault, souther... Available to Purchase
in Rupture Propagation and Ground Motion of Strike‐Slip Stepovers with Intermediate Fault Segments
> Bulletin of the Seismological Society of America
Published: 16 December 2014
Figure 1. The Claremont–Casa Loma stepover of the northern San Jacinto fault, southern California: a real‐world example of a stepover with an intermediate fault strand between the primary segments. The rightmost strand is the Claremont, and the leftmost is the Casa Loma. The small fault between
Image
Close up of the northern SJF zone with geometry based on the U.S. Geologi... Available to Purchase
in Rupture and Ground‐Motion Models on the Northern San Jacinto Fault, Incorporating Realistic Complexity
> Bulletin of the Seismological Society of America
Published: 28 July 2015
Figure 2. Close up of the northern SJF zone with geometry based on the U.S. Geological Survey (USGS) Quaternary Faults Database (see Data and Resources ). The Claremont–Casa Loma stepover is circled in green. The Claremont strand is the more northeasterly of the two; the Casa Loma
Journal Article
Rupture and Ground‐Motion Models on the Northern San Jacinto Fault, Incorporating Realistic Complexity Available to Purchase
Publisher: Seismological Society of America
Published: 28 July 2015
Bulletin of the Seismological Society of America (2015) 105 (4): 1931–1946.
...Figure 2. Close up of the northern SJF zone with geometry based on the U.S. Geological Survey (USGS) Quaternary Faults Database (see Data and Resources ). The Claremont–Casa Loma stepover is circled in green. The Claremont strand is the more northeasterly of the two; the Casa Loma...
FIGURES
Includes: Supplemental Content
Image
Example paths of rupture propagation given earthquake initiation points (st... Available to Purchase
in Rupture Passing Probabilities at Fault Bends and Steps, with Application to Rupture Length Probabilities for Earthquake Early Warning
> Bulletin of the Seismological Society of America
Published: 18 May 2021
, western star) begins at the Casa Loma stepover then transitions to the SAF either directly, or by a short section of the Lytle Creek fault. Rupture may also extend south from the Casa Loma starting point. The color version of this figure is available only in the electronic edition.
Image
The fault strength parameter S for a N7°E‐oriented regional stress field ... Available to Purchase
in Rupture and Ground‐Motion Models on the Northern San Jacinto Fault, Incorporating Realistic Complexity
> Bulletin of the Seismological Society of America
Published: 28 July 2015
to relative low S . The actual S value on most parts of the fault is not equal to the input S value. The Claremont strand has less variation in S overall than the Casa Loma strand does, and the bands of particularly high or particularly low S are wider on the Casa Loma strand than on the Claremont
Journal Article
Broadband Ground Motions from Dynamic Models of Rupture on the Northern San Jacinto Fault, and Comparison with Precariously Balanced Rocks Available to Purchase
Publisher: Seismological Society of America
Published: 07 July 2015
Bulletin of the Seismological Society of America (2015) 105 (4): 1947–1960.
... and Resources ). The Claremont strand is shown in blue, the Farm Road strand in red, and the Casa Loma–Clark strand in black. Other strands of the SJF are shown in yellow, and other Quaternary faults are shown in gray. The cities are indicated with blue dots. The area of the present study is enclosed...
FIGURES
Includes: Supplemental Content
Image
UCERF3‐based rupture length probabilities for rupture with one end at the S... Available to Purchase
in Rupture Passing Probabilities at Fault Bends and Steps, with Application to Rupture Length Probabilities for Earthquake Early Warning
> Bulletin of the Seismological Society of America
Published: 18 May 2021
fault model 3.1 having one end at the Casa Loma step of the SJF (west star, Fig. 6 ). (b) The solid line is corresponding complementary cumulative distribution (CCD) (solid line) of rupture length for ruptures in (a). Dashed line shows the length CCD for the fraction of ruptures starting at the step
Image
Mesh of the SJF , generated with FaultMod ( Barall, 2009 ), as used in our... Available to Purchase
in Broadband Ground Motions from Dynamic Models of Rupture on the Northern San Jacinto Fault, and Comparison with Precariously Balanced Rocks
> Bulletin of the Seismological Society of America
Published: 07 July 2015
Figure 3. Mesh of the SJF , generated with FaultMod ( Barall, 2009 ), as used in our dynamic models. The parts of the fault that are able to rupture are marked in white. The Claremont strand is to the left in this figure, the Casa Loma to the right, and the Farm Road is between them. The grid
Image
Map of the San Jacinto fault ( SJF ) zone, with a geometry based on the U.S... Available to Purchase
in Broadband Ground Motions from Dynamic Models of Rupture on the Northern San Jacinto Fault, and Comparison with Precariously Balanced Rocks
> Bulletin of the Seismological Society of America
Published: 07 July 2015
Figure 1. Map of the San Jacinto fault ( SJF ) zone, with a geometry based on the U.S. Geological Survey (USGS) Quaternary faults database (USGS, 2010; see Data and Resources ). The Claremont strand is shown in blue, the Farm Road strand in red, and the Casa Loma–Clark strand in black. Other
Journal Article
Strain accumulation on the San Jacinto fault near Riverside, California Available to Purchase
Publisher: Seismological Society of America
Published: 01 October 1976
Bulletin of the Seismological Society of America (1976) 66 (5): 1749–1754.
... and Hemet (Figure 1). The area covered is the San Jacinto Valley, which appears to be a graben bounded on the southwest by the Casa Loma fault and on the northeast by the Claremont fault. The Claremont fault is apparently the currently active strand of the San Jacinto fault in this area. The geologic...
Image
Geometric and cumulative penalties at subsection boundaries for rupture nor... Available to Purchase
in Rupture Passing Probabilities at Fault Bends and Steps, with Application to Rupture Length Probabilities for Earthquake Early Warning
> Bulletin of the Seismological Society of America
Published: 18 May 2021
for an alternate path where the SJF connects directly to the SAF directly from the San Bernardino strand of the SJF. (d) Conditional probability of rupture length unilaterally southeast from the Casa Loma starting point. The fault‐geometric estimate of probability of any length bilateral rupture is the product
Journal Article
Historic earthquakes (1918 to 1923) and an assessment of source parameters along the San Jacinto fault system Available to Purchase
Publisher: Seismological Society of America
Published: 01 August 1992
Bulletin of the Seismological Society of America (1992) 82 (4): 1786–1801.
..., indicating locations on the San Jacinto fault system. Rasmussen (1981) has suggested that the December 1899 (M ~ 7.1) event produced significant surface rupture along the northeastward-dipping Casa Loma fault (Fig. 2). He believes the 1918 (M ~ 6.8) event may have ruptured 1788 D. I. DOSER 117.1 33.9N...
Journal Article
Estimating Locations and Magnitudes of Earthquakes in Southern California from Modified Mercalli Intensities Available to Purchase
Publisher: Seismological Society of America
Published: 01 August 2006
Bulletin of the Seismological Society of America (2006) 96 (4A): 1278–1295.
... 20 km southeast of, the San Gorgonio section of the San Andreas fault. Triggered slip appears to be a characteristic of the San Jacinto fault zone ( Burford, 1972 ; Hudnut and Clark, 1989 ). In the San Jacinto Valley, the San Jacinto fault zone comprises two major faults, the Casa Loma fault...
FIGURES
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